Levitov, Leonid

Wednesday September 21, 2011
Time: 9:30
Place: HPF G 6
Host: Klaus Ensslin

States with spontaneously broken time reversal symmetry in graphene

Leonid Levitov
MIT, Cambridge, USA

This talk will describe recent prediction of chiral superconductivity from repulsive interactions in doped graphene [1]. Chiral superconductivity involves a pairing gap that winds in phase around the Fermi surface, breaking time reversal symmetry. This exotic phase is realized at a specific level of doping, where the density of states is singular, strongly enhancing the critical temperature Tc. At this doping level, the Fermi surface is nested, allowing superconductivity to emerge from repulsive electron-electron interactions. We show using a renormalization group method that superconductivity dominates over all competing orders for any choice of weak repulsive interactions. Superconductivity develops in a doubly degenerate, spin singlet channel, and a mean field calculation reveals that the superconductivity is chiral d + id. We therefore predict that doped graphene will provide the first experimental realization of spin-singlet chiral superconductivity.

R. Nandkishore, L. Levitov, A. Chubukov, arXiv:1107.1903